1. Field of the Invention
This invention relates to the field of vent valves, and more particularly, to a vent valve assembly used in heart surgery.
2. Prior Art
During heart surgery, a drainage cannula is often inserted into the heart, and more specifically, into the left ventricle. This cannula is used to drain the blood either by gravity flow or in combination with a pump. The blood is directed through one or more conduits to a cardiotomy reservoir, and then to an oxygenator which oxygenates the blood. Blood flow is then directed back to the patient. It has been found in connection with such a system, that certain advantages can be gained by decompressing the left ventricle during the cardiopulmonary bypass procedure. One of the problems associated with pump drainage is excessive suction. While the amount of suction can be increased, too much suction can cause the conduits to collapse should the drainage cannula become occluded. Even though this problem has been recognized for some time, the solution has proved elusive.
The prior art is well aware of many valve configurations which have been used in a wide variety of medical products as well as in connection with automotive products, and the like. Examples of such valves are disclosed in U.S. Pat. Nos. 3,556,122; 3,572,375; 3,626,978; 3,633,613; 3,661,174; 3,818,929; 3,905,382; 3,941,149; and 4,084,606. Notwithstanding the existance of these different valve configurations, there is no prior art device which has all of the features associated with the overpressure safety valve of the present invention.